The present invention is directed toward dual mode satellite/terrestrial mobile terminals and, more particularly, toward a method for interpreting LOCI data in dual mode satellite/terrestrial mobile terminals.
Dual mode satellite/terrestrial mobile terminals currently exist in the prior art, and generally include dual mode satellite/GSM (Global System for Mobile Communications) and satellite/AMPS (Advanced Mobile Phone System) mobile terminals. Location information is utilized in dual mode phones to uniquely identify the location of the mobile terminal within a particular communications system, whether it be terrestrial (GSM or AMPS) or satellite. A problem that often arises in conventional dual mode phones occurs in the handling of location information when the mobile terminal transitions between the different modes of operation. In particular, problems in the handling of location information typically occur with the dual mode phone in the satellite mode after transitioning from the terrestrial mode. Typical problems which occur in such dual mode mobile terminals include (a) the inability to uniquely identify locations areas, (b) the inability to resume satellite inclined orbit operations upon transitioning from the GSM mode, and (c) the inability to handle location information associated with the satellite mode of operation.
Dual mode mobile terminals typically implement shared usage of LOCI information on a SIM card in the mobile terminal. LOCI information is information related to the particular location of the mobile terminal, while the SIM card is a removable smart card containing a nonvolatile memory and logic which contains user subscription data. In the GSM mode, the mobile terminal LOCI information includes a PLMN/LAC pair stored on the SIM card to uniquely identify a location in GSM. The PLMN (Public Land Mobile Network) identifies a network service provider with which the mobile terminal last registered, such as, Bell Atlantic, MCI, etc., while the LAC (Location Area Code) identifies a location area within the network with which the mobile terminal last registered.
In the satellite mode, the mobile terminal LOCI information includes a PSMN/LAC pair to uniquely identify a location in the satellite system, and a PLMN/LAC pair to identify a gateway for call routing purposes. The PSMN (Public Satellite Mobile Network) identifies a satellite system with which the mobile terminal last registered. The LAC (Location Area Code) in the PSMN/LAC pair uniquely identifies a location within the satellite system with which the mobile terminal last registered. This mismatch in LOCI information in satellite and GSM modes creates problems which are compounded by how this location information is received and stored at the mobile terminal.
LAC information is received by the mobile terminal on the control channel (BCCH) in both GSM and satellite modes. However, since LAC codes are not unique to a particular network, this information is not sufficient to identify a location change of the mobile terminal. Both the LAC code and the network code (PLMN or PSMN) are required in the LOCI information to properly identify a location change of the mobile terminal. However, the network code in the LOCI information has different meanings in GSM and satellite modes of operation. The PSMN code is the satellite equivalent of the GSM PLMN code, with both codes received by the mobile terminal on the control channel. However, with the mobile terminal in the satellite mode, the PSMN code is not stored on the SIM card along with the corresponding LAC code. Instead, a PLMN code identifying a gateway for routing calls is stored on the SIM card. This PLMN gateway code is not received on the satellite control channel, but rather is transmitted by the satellite during the location update procedure. Thus, the PLMN gateway code is not available to determine whether a location update of the mobile terminal is necessary. As long as the mobile terminal remains in the satellite mode, this is not a problem. However, once the mobile terminal transitions to the GSM mode and performs a location update, the LOCI information (PLMN and LAC fields) have GSM values. Should the mobile terminal transition back to the satellite mode while in the same satellite network, i.e., same PSMN, only the LAC code is present to determine if mobile terminal has changed location. This is insufficient for proper location updating of the mobile terminal.
The present invention is directed toward overcoming one or more of the above-mentioned problems.
A method of interpreting location area information data in a satellite/terrestrial dual mode mobile terminal is provided, with the mobile terminal in the satellite mode and communicating with a satellite system. The method includes the steps of determining whether a most recent registration of the mobile terminal was accomplished in the satellite or terrestrial mode and, if it is determined that the most recent registration of the mobile terminal was accomplished in the terrestrial mode, then determining if (1) a satellite operator ID broadcast by the satellite system matches a satellite operator ID from a most recent satellite location update of the mobile terminal, and (2) a satellite beam pair in a satellite spotbeam pair list broadcast by the satellite system matches a satellite beam pair in a satellite spotbeam ID from a most recent satellite location update of the mobile terminal. If matches are found at both steps (1) and (2), then mobile terminal initiates a location update with the satellite system in the matching satellite beam pair determined at step (2).
If matches are not found at either steps (1) and/or (2) above, then the mobile terminal initiates a location update with the satellite system in the satellite spotbeam ID broadcast by the satellite system.
If it is determined that the most recent registration of the mobile terminal was accomplished in the satellite mode, then the method further includes the steps of determining if (3) an update status flag stored in the mobile terminal indicates that the mobile terminal does not need to perform a location update, and (4) a satellite operator ID broadcast by the satellite system matches a satellite operator ID from a most recent satellite location update of the mobile terminal. If either answer at steps (3) or (4) above is no, then the mobile terminal initiates a location update with the satellite system in the satellite spotbeam ID broadcast by the satellite system.
If the answers at both steps (3) and (4) above are yes, then the method further includes the step of determining if (5) a satellite spotbeam ID broadcast by the satellite system matches a satellite spotbeam ID from a most recent satellite location update of the mobile terminal and, if a match is found at step (5), then indicating that no location update of the to mobile terminal is necessary.
If the satellite spotbeam ID broadcast by the satellite system does not match a satellite spotbeam ID from a most recent satellite location update of the mobile terminal at step (5), then the method further includes the step of determining if (6) a satellite beam pair in a satellite spotbeam pair list broadcast by the satellite system matches a satellite beam pair in the satellite spotbeam ID for the most recent satellite location update of the mobile terminal. If a match is found at step (6), then the method further includes the steps of determining if (7) a satellite spotbeam ID of the spotbeam last serving the mobile terminal matches the satellite spotbeam broadcast by the satellite system and, if a match is found at step (7), then indicating that no location update of the mobile terminal is necessary.
If the satellite spotbeam ID of the spotbeam last serving the mobile terminal does not match the satellite spotbeam ID broadcast by the satellite system at step (7), then the method further includes the steps of (8) replacing, at the mobile terminal, (a) the satellite spotbeam ID of the spotbeam last serving the mobile terminal with the satellite spotbeam ID broadcast by the satellite system, and (b) the satellite beam pair list associated with the spotbeam last serving the mobile terminal with the satellite beam pair list broadcast by the satellite system.
If it is determined that the satellite beam pair in the satellite spotbeam pair list broadcast by the satellite system does not match the satellite beam pair in the satellite spotbeam ID from the most recent satellite location update of the mobile terminal at step (6), then the method further includes the steps of determining if (9) a satellite beam pair in the satellite spotbeam pair list broadcast by the satellite system matches the satellite beam pair in a satellite spotbeam ID of the spotbeam lasting serving the mobile terminal. If a match is found at step (9), then initiating a location update of the mobile terminal with the satellite system in the matching beam pair.
If the satellite beam pair in the satellite spotbeam pair list broadcast by the satellite system does not match the satellite beam pair in the satellite spotbeam ID of the spotbeam last serving a mobile terminal at step (9), then the method further includes the step of initiating a location update of the mobile terminal with the satellite system in the satellite spotbeam ID broadcast by the satellite system.
The present invention provides a method of storing and interpreting location information data in dual mode satellite/terrestrial mobile terminal with little change to the location update procedure, or to the SIM data with the mobile terminal in the terrestrial mode.
The present invention supports the current arrangement for standard GSM SIM cards and various other possible arrangements for LOCI data in dual mode mobile terminals.
Other aspects and advantages of the present invention can be obtained from a study of the application, the drawings, and the appended claims.